This invention relates generally to improvements in methods and apparatus for producing animation data and, more particularly, to a new and improved system for production of enhanced rotary animation data.
Heretofore, in producing an animation product by conventional manual techniques, it has generally been customary to execute the steps of first determining the total number of required animation frames for smoothing the motion of a desired animation product from the beginning to the end thereof, and then producing the individual pictures for the entire sequence of required frames. However, considerable time and effort are needed to produce all of the animation pictures for the entire frame sequence.
More recently, there have been methods of producing an animation product by adapting the technique of computer graphics. This approach is remarkably effective, particularly for production of three-dimensional animation.
One of the methods for producing animation data through use of such computer graphics is a method of key frame interpolation. In accordance with this latter method, a user regards pictures of principal change points as key frames in a desired animation sequence, and produces only the pictures of such key frames.
Generally, a key frame is formed by an operator with a three-dimensional layout of the picture of each component element (hereinafter referred to as an object) in the animation. Picture data of such objects are prepared as model data in a memory or the like and can be read out therefrom by the operator for use as needed. The model data may be expressed in either two-dimensional or three-dimensional terms.
Frames of transitional animation data, i.e., interpolation frames between the key frames, are formed automatically through an interpolation process by utilizing the correlation between the objects in adjacent key frames which precede and follow the interpolation frames in the sequence of frames. More specifically, when the objects included in the preceding and following adjacent key frames, anterior and posterior, respectively, to the interpolation frames have been displaced or rotated, the displaced positions or rotational changes of the objects in the interpolation frames between the two key frames are calculated through an interpolation process from the data of the objects included in the preceding and following key frames. Such an interpolation process is executed with respect to each of the objects in the animation.
Thus, it becomes possible to produce animation data having relatively smooth and continuous motions in three-dimensional space. Accordingly, in an animation data producing apparatus based on the afore-described technique of computer graphics, a series of animation data can be produced with relative ease by merely controlling the picture data of only the key frames.
In a method of producing an animation where any change of an object between two key frames is such that a two- or three-dimensional object is rotated around an axis in a three-dimensional space, the following related prior art is known with regard to an interpolation process for an object in an interpolation frame.
Generally, the rotation of an object in a three-dimensional space is expressed through decomposition or resolution into rotational angle components around an X-axis, a Y-axis and a Z-axis which are three coordinate axes for representing the three-dimensional space. That is, the rotation is expressed through decomposition into the angle component around the X-axis, the angle component around the Y-axis and the angle component around the Z-axis. Although the rotation may also be expressed in polar coordinates depending on some specific application, this is rather rare in the related art.
In the animation data producing apparatus of the prior art, interpolation data of each object in the interpolation frame is obtained by first interpolating the rotational angle components around the X-, Y- and Z-axes independently of one another and then compositing such components.
However, according to a method of producing rotary animation data in the animation producing apparatus of related art, the rotational angle components around the X-, Y- and Z-axes are interpolated independently of one another, so that the rotation is rendered different from what was actually intended by the animator and, therefore, the animation rendition becomes unnatural.
This disadvantage occurs because the rotation of the object is interpolated while the rotation components thereof around the X-, Y- and Z-axes are processed as independent and linear.
More specifically, in accordance with the positions of an interpolation frame and two key frames anterior and posterior thereto, the rotation angle in that interpolation frame (the rotation angle at the intermediate position between the two key frames) is determined. If the rotation angles around the X-, Y- and Z-axes are determined independently of one another, the rotation in each interpolation frame becomes such that the rotation axes of the object are rendered mutually different in the individual interpolation frames.
Because there exists no correlation among the X-, Y- and Z-axes and, even in the case of linear rotation around each axis, the rotation in each interpolation frame obtained by compositing the mutually independent rotation components around the three axes is also rendered independently in each frame.
In this regard, since the rotation is performed while the axis thereof is being changed as described, if an interpolation frame between a first key frame and a second frame is formed by the animation data producing method of the related art, the resultant animation is such that the rotational locus thereof is different from a natural rotary motion around one axis between the first key frame and the second key frame and is therefore unnatural in its rendition.
Accordingly, there has been a long existing need for enhanced accuracy, efficiency and more natural rendition in image processing for generation of interpolation frames between key frames of an animation sequence, and particularly where rotary animation data is involved. The present invention fulfills these needs.